Main bondage

[KAS1]

Why is this not a simple thing for people to get their heads around. It's so simple, the 0.05ohms is just a recommended value between two or more conductive parts ie pipes or steel structure which may or may not be connected together by a BONDING CONDUCTOR and the MAIN BONDING CONDUTOR'S resistance is dependant on the size and length of the cable , which should be determined by calculation and/or the size of the EARTHING CONDUCTOR simple. I REPEAT THE 0.05ohms HAS NOTHING TO DO WITH THE MAIN BONDING CONDUCTOR'S resistive value. The main bonding conductor is from the MET to a pipe or steel structure and a bonding conductor is between two pipes or metalwork that requires bonding to met the requirements of BS7671.

 

[Guest55]

so bonding all extraneous services using a single protective conductor by-passes the whole problem by ensuring zero potential between each point and the 0.05 argument falls flat on its face lol.
;-)

 

[Geoffsd]

And MAIN bonding only goes from entry point to MET.

 

[KAS1]

This thread has been going so long I forget how the Main Bonding Conductor was measured did he say he used a wandering lead which was only 0.05mm in diameter lol

 

[Geoffsd]

Why is this not a simple thing for people to get their heads around. It's so simple, the 0.05ohms is just a recommended value between two or more conductive parts

No it's the recommended value of the main bond - entry point to MET.
There is no requirement to 'supplementary bond' incoming services.
Obviously if they are close one conductor can be used but that is coincidental.

ie pipes or steel structure which may or may not be connected together by a BONDING CONDUCTOR and the MAIN BONDING CONDUTOR'S resistance is dependant on the size and length of the cable , which should be determined by calculation and/or the size of the EARTHING CONDUCTOR simple.

And IF calculated at more than that because of length of run then larger conductor would be required.

I REPEAT THE 0.05ohms HAS NOTHING TO DO WITH THE MAIN BONDING CONDUCTOR'S resistive value.

YES it does because you are measuring from MET to point of bond - i.e. the conductor - as the pipe may have no other connection to the MET.

The main bonding conductor is from the MET to a pipe or steel structure

Quite.

and a bonding conductor is between two pipes or metalwork that requires bonding to met the requirements of BS7671.

Supplementary bonding - yes - for which there is no requirement between such parts unless in a special location, not under the floorboards.

 

[Gavin A]

And MAIN bonding only goes from entry point to MET.

but it goes from entry point of both pipes to MET, therefore both pipes are effectively bonded together via the MET (or sometimes by sharing the same bonding cable to the MET).

btw, this was the post I was referring to, which KAS1 also agreed with.

The 0.05 value is the value below which potential difference should be, between simultaneously accessible extraneous conductive parts. Example of which is a gas pipe and a water pipe next to each other. Test between the two.

Even if both are 10mm bonded individually back to MET, if the difference between the two is greater than 0.05 then they need to be bonded to each other.

The 0.05 figure is not a value to be achieved between MET and bonding point taking into account the value of resistance of the cable.

That is how I understand it, of course, I am open to other more enlightened people's wisdom.

Regards.

my point being that if you do need to achieve a 0.05ohms reading between gas and water pipes as this post suggests, then logically this is not going to be achieved if one of your bonding cables has a reading above 0.05ohms itself, certainly not if it has a 0.25ohms reading.

I've not actually got the 7671 at home to check if the above statement is actually right or not, I'm just questioning how that statement can be squared with statements that the main bonding cables themselves don't need to achieve a 0.05ohms reading as KAS1 in particular has been saying (and KAS1 agreed with the statement quoted). If the statement I've quoted is actually wrong, then fair enough, but the 2 statements seem to be incompatible to me, yet both are being made or agreed with by the same posters.

 

[KAS1]

I rest my case.............................. I understand the requirements I just have to except not all other do..........................

 

[Gavin A]

This thread has been going so long I forget how the Main Bonding Conductor was measured did he say he used a wandering lead which was only 0.05mm in diameter lol

I don't think the OP has answered the question in the 2nd post about whether he zeroed the tester before carrying out the test, which would obviously make the rest of the thread a bit irrelevant if it hadn't been done.

 

[KAS1]

Candidates are still incorrectly stated that the maximum value for the resistance of a main protective bonding conductor is 0.05 ohms. This value is applicable where access to the bonding connection is not possible and a test is made between two extraneous conductive parts (GN3 Page 35). This value is not the maximum permitted resistance of the main protective bonding conductor.

THIS IS ONE OF THE MOST FAILED QUESTIONS IN TEST AND INSPECTION EXAMS when the question has been asked state the maximum value of resistance of a main protective bonding conductor...................I REST MY CASE END OF FINISH

 

[Gavin A]

Candidates are still incorrectly stated that the maximum value for the resistance of a main protective bonding conductor is 0.05 ohms. This value is applicable where access to the bonding connection is not possible and a test is made between two extraneous conductive parts (GN3 Page 35). This value is not the maximum permitted resistance of the main protective bonding conductor.

THIS IS ONE OF THE MOST FAILED QUESTIONS IN TEST AND INSPECTION EXAMS when the question has been asked state the maximum value of resistance of a main protective bonding conductor...................I REST MY CASE END OF FINISH

OK, but how do you achieve that 0.05ohms reading between 2 ET parts if the figure for the bonding cable itself between one of them and the MET is higher than 0.05ohms?